You can provide multiple .hlp files instead of a single .hlp file. You must set configuration options to ensure the links between .hlp files work as expected. See:
§8.4.2 Specifying cross-reference destination files
§8.13.2.5 Referencing multiple help files from contents
As an alternative, you can provide a main .hlp file with contents entries that link to other .hlp files; see §7.11 Setting up a dynamic modular Help system.
For more information, see Designing your Help system > Planning your Help system > Designing for multiple Help files in Help Workshop Help Topics: Help Author’s Guide.